We're always pleased to see developer resources pop up around the web that help keep things ticking long. Over at Templarian (Austin Andrews), an icon pack full of superb quality graphics has been in the works (with more being added), which is licensed under Creative Commons license. Should you require an icon that's not present, one can either create and submit the icon for the pack or request it from the author. The icons are available in black and white variants.
Andrews wants developers to take care when designing apps on the platform, and we (as consumers) are on the same wave length. Metro UI is slick and clean and developers should take advantage of this.